Scanning a file

Bengt Richter bokr at
Mon Oct 31 17:18:19 CET 2005

On Mon, 31 Oct 2005 09:41:02 +0100, =?ISO-8859-1?Q?Lasse_V=E5gs=E6ther_Karlsen?= <lasse at> wrote:

>David Rasmussen wrote:
>> If you must know, the above one-liner actually counts the number of 
>> frames in an MPEG2 file. I want to know this number for a number of 
>> files for various reasons. I don't want it to take forever.
>Don't you risk getting more "frames" than the file actually have? What 
>if the encoded data happens to have the magic byte values for something 
Good point, but perhaps the bit pattern the OP is looking for is guaranteed
(e.g. by some kind of HDLC-like bit or byte stuffing or escaping) not to occur
except as frame marker (which might make sense re the problem of re-synching
to frames in a glitched video stream).

The OP probably knows. I imagine this thread would have gone differently if the
title had been "How to count frames in an MPEG2 file?" and the OP had supplied
the info about what marks a frame and whether it is guaranteed not to occur
in the data ;-)

Bengt Richter

More information about the Python-list mailing list